razor-edge
n (also ,razor´s `edge) (fig 比喻)
1 sharp line of division 明显的分界线
a razor-edge of difference between genius and madness 天才和疯狂之截然不同.
2 (idm 习语) on a razor-edge/razor´s edge in a dangerous or critical situation 处於危险的境地; 处於紧要关头
Since he escaped from gaol, Tom has been living on a razor´s edge, terrified of recapture. 汤姆越狱後, 时时如惊弓之鸟, 生怕再次被捕.